work around chrome regression (https://code.google.com/p/chromium/issues/detail?id=413795) that broke dragging blocks
fix detection of enter key in text filter (cf https://groups.google.com/forum/#!topic/reactjs/ZTGDLGpuFog)
fix issue where anonymous users could drag an image and trigger block dragging
Merge pull request #455 from ENCODE-DCC/1850-fix-anon-dragging

fix layout editor issues